Field of the Invention
The present invention relates to technology to correct image blur that occurs when performing a panning shot in an image capturing apparatus.
Description of the Related Art
Conventionally, a technique called a panning shot is known as a shooting technique that expresses a feeling of speed of a moving object. This shooting technique, by a user panning a camera according to movement of an object, aims to stop motion of the moving object while allowing a background to flow. When shooting a panning shot, it is necessary for the user to pan the camera according to movement of the object, but if the panning speed is too fast or too slow, a difference may occur between the moving speed of the object and the panning speed. In this case, the object whose motion the user wishes to stop within a screen often is blurred in a resulting image.
In order to solve this problem, the following sort of technology is disclosed in Japanese Patent Laid-Open No. 4-163535. That is, based on a “relative angular velocity of the object relative to the image capturing apparatus calculated before exposure”, and an “angular velocity of the image capturing apparatus during exposure obtained from an angular velocity sensor”, part of an optical system of a lens or an image capturing unit is moved to correct blurring of the object (object blur) during exposure. The relative angular velocity of the object relative to the image capturing apparatus is calculated from a “moving amount on the image plane of the object detected from temporally consecutive images” and “output of the angular velocity sensor”.
However, according to the conventional technology disclosed in above Japanese Patent Laid-Open No. 4-163535, it is assumed that the movement of the object before exposure is not significantly different than the movement of the object during exposure. For example, in a case where the object is a person who is walking (including a person who is running), because the body of the person moves back and forth vertically, even if the above assumption is satisfied in the traveling direction, this assumption is not satisfied for a direction orthogonal to the traveling direction. In other words, relative to the image capturing apparatus, an object that was moving downward during movement detection of the object before exposure may move upward in the opposite direction during exposure. In this case, if blur correction is performed without modification, there are cases where correction is performed in the opposite direction (opposite correction), resulting in an image that is even more blurred.
FIGS. 13A and 13B are graphs showing changes in angular velocity in the vicinity of the face of a walking person, as an example. In these graphs, the horizontal axis indicates time and the vertical axis indicates angular velocity. FIG. 13A is a graph of angular velocity change in the horizontal direction of a walking person, and here the angular velocity gradually increases, but is moving in one direction. On the other hand, FIG. 13B is a graph of angular velocity change in the vertical direction of a walking person, and the person who is the object is moving downward during detection of angular velocity, but is moving upward during exposure. In this case, a correction method as described in Japanese Patent Laid-Open No. 4-163535 cannot be used.